System for remotely controlling the frequency of an oscillator circuit



' Se t. 29, 1936. P. D. LOWELL 2,056,011

SYSTEM FOR REMOTELY CONTROLLING THE FREQUENCY OF AN OSCILLATOR CIRCUITFiled July 25, 1933 v 41 5 WK Du QO/WM Patented Sept. 29, 1936 FQPATEENTOFFICE.

SYSTEM 'FOR REMOTELY "CONTROLLING THE "FREQUENCY OF AN OSCILLATORCIRCUIT Percival .D. 1 Lowell, Chevy-.Chase, Md.,- assignor to RadioCorporation ofAmerica, New :Xork, N. Y., a corporation of DelawareApplication July 25, 1933, Serial No. 682,131

6Claims. (Cl. 250-20) 7 -My.invention relates broadly to improvementsinradio receiving circuits and more particularly to a meansfor-controlling thefrequ'ency of an oscillator circuit from a remotecontrol position.

[One of the objects "of "my invention-is to provide asystem for remotelycontrolling the frequency-of an oscillator circuit for effecting ashiftin the frequency'ofsuch oscillator circuit within predeterminedlimits.

Another object of my invention is to'provide a circuit arrangement forremotely controlled radio-receiving stations in which the operator atthe remote control-station may readily control the beat note frequencyof the incoming signaling energy from the remote control station.

Still another object of-my invention is to pro- Vi'de acircuit-arrangement ina radio receiving system for controlling theoperating frequency of an oscillator locatedatthe signal receivingstation by line wire from a remote point wherein potential for theoperation of the oscillator is supplied from 'a sourcelocated at theremote point 'over the same wires which conduct the signal 'energyfromthe receiving station to the remote control station.

.A further-object of my invention'is to provide anarrangement of signalreceiving system including a radioreceiving station and a remote controlstation interconnected by line wire over which the received radiosignals are transmitted to-the: control station and wherein theoscillator at:thereceiving'station has the frequencythereof..-controlled directly from the remote control station over thesame wires which transmit the signaling: energy to-the-remote controlstation.

A still further: object of my invention is to provide a systemforremotely controlling the frequency ofvan oscillator circuit by adjustingthe plate potential suppliedto the oscillator circuit forcorrespondingly shifting the frequency of the. oscillator circuit withinpredetermined limits. .Dther andtfurther objectsof my invention residein a circuit arrangement for a remote control system: .employing a highfrequency oscillator with means at the control point for adjustingthefrequency of the oscillator asset forthrmore fully in thespecification (hereinafter following by reference to the accompanyingdrawing which diagrammatically land schematically illustrates myinvention.

v-My invention -'is particularly useful, for example,':when: it isdesired'that a radioreceiver be used: for the reception of continuouswave .radio telegraphic vcodel'signals. In this case,:it is. mostdesirable to employ an electron tube oscillator for obtaining the audiofrequency beat-note. 'To obtain the proper pitch 'of this'beat note itis necessary to provide a means for varying the frequencyof theoscillatorover a limited range, this means being commonly called avernier adjustment. It is'the' purpose of-my invention to provide asimple and suitable meansof obtaming I this Vernier adjustment eitherfrom a position close .to' the receiver-or from-a position located -asubstantial distance away from the 10 receiver. a

My invention makes use of the fact that the frequency of anelectrontubeoscillator changes when the voltage impressed on the plate of theelectron tube is changed. This is due to the fact that the changeinplate voltagecausesa change in the plate impedance which in turnreflects backtinto the grid or input circuit, causing a change in theinput capacity, the latter causing the frequencyrof the oscillations to'change. My t invention provides a method of deliberately vary ing theplate voltage of the oscillator thereby indirectlycausing a variation ofthe frequency emitted .by the oscillator over a limited range sufiicientto selectively adjust the .pitch .of :the heatnote frequencysto'ithedesireddegree. My invention provides means for effecting ithe :vernierdistant tuning control ofassuperheterodyne receiver, inwhichtthefrequency converting oscillator is provided with means forchangingtheoscillatorfrequency by varying the plate voltage from a distantposition.

Referring to the drawing which diagrammaticallyshowsmy invention, Arepresentstheloca- :tion of'thereceiving. apparatus,- a portion of whichincludesan electron tube oscillating circuit comprising .electron tubeI, inductance and capacity 2, grid condenserB, leak 4, sourceof theatervoltage-5, grid circuit feedback coil 6 and thecbypass condenser 8connected-across the leadsrzfl-which extend to the remote controlstation through the signal conductors 2] tothe source of potential 1.-At the distant control-position B, a; potentiometer l8 isprovided, inshunt to thesource of potential Tfor. controlling the efiE-ective;potential impressed upon:the plate circuitof the oscillator -l atstation A. By moving theslider or adjustable taps .ofpotentiometer [8,the voltage impressedjon the .plate of the oscillator is caused-to vary,thereby causing-the oscillationzfrequency to-correspondd ingly varywithin predeterminedlimits as desired. .The direct current supplied bythe .potential sourceJ-is selected by potentiometer: L8 and-passedthrough leads r28land audio fnecuency. choke coils .jll to the lineconductors-2] adjacentcthei entrance of the conductors into distantcontrol station B. At the opposite end of the line adjacent the stationA, the leads 20 connect to conductors 2! through audio frequency chokecoils H. The receiving apparatus at station A has been schematicallyshown at I2 connected with the antenna ground system indicated at M. Theoutput of the audio frequency signal channel is represented at I5connected to the primary winding of audio frequency transformer l6having a secondary winding I! connected through blocking condensers l9to line conductors 2|. The opposite end or the line conductors 2|connect through blocking condensers 22 interposed between line 2| andthe primary winding 23 of audio frequency transformer 24. Thesecondarywinding 25 of transformer 24 connects to the input of audiofrequency amplifier 26, the output of which connects to the signalindicating means such as telephone headset 21. line conductors block thepassage of direct current from source 1 but permit the audio frequencysignal current to pass therethrough from station A to station B. Thechoke coils I0 and I l in leads 28 and 20 prevent the passage of audiofrequency signal currents from the signal line to the plate circuit ofthe oscillator or to the direct current supply system. The arrangementpermits the use of the same line wire system for both the audiofrequency signal impulses from the receiver and the plate supplypotential for the oscillator.

While I have illustrated the source of potential for controlling thefrequency of the oscillator as located at the control station E, Idesire that it be understood that the source of potential may be locatedat station A and the effect thereof upon oscillator l regulated by theadjustment of potentiometer I 8. It will be observed that the radiofrequency path through the oscillator is completed at station A throughbypass condenser 8 and under no circumstances will the high frequencyenergy tend to pass through leads 20. The direct current is conductedthrough leads 2!] independently of the high frequency oscillations whichare confined to the immediate circuits of the oscillator I.

It is understood, of course, that the oscillator can be used for manyother purposes than those here disclosed either in conjunction withradio receivers ortransmitters or any other purposes where a remotelycontrolled Vernier tuning of an oscillator is required. While I havedescribed my invention in one of its preferred embodiments I desire thatit be understood that modifications may be made and that no limitationsupon my invention are intended other than those which are imposed by thescope'of the appended claims.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is as follows:

1. In a remote control system, a receiving station, a remote controlstation, a line wire circuit extending therebetween for transmittingaudio frequency signals from said receiving station to said remotecontrol station, signal indicating means at said remote stationconnected with said line wire circuit for reproducing the signalstransmitted from said receiving station, a beat frequency oscillator atsaid receiving station, connections between said oscillator and saidline wire circuit, variable control means including a source ofpotential at said remote control station, connections between saidvariable control means and said line wire circuit, and elements in eachof the aforesaid connections for preventing the passage The condensersl9 and 22 in the of audio frequency signal energy into said beatfrequency oscillator at said receiving station or into said variablecontrol means at said remote control station.

2. In a remote control system, a receiving station, a remote controlstation, a line wire circuit extending therebetween for transmittingaudio frequency signals from said receiving station to said remotecontrol station, signal indicating means at said remote stationconnected with said line Wire circuit for reproducing the signalstransmitted from said receiving station, a beat frequency oscillator atsaid receiving station, connections between said oscillator and saidline wire circuit, variable control means including a source ofpotential at said remote control station, connections between saidvariable control means and said line wire circuit, and audio frequencychoke coils disposed in each of the aforesaid connections for preventingthe passage of audio frequency signal energy into said beat frequencyoscillator at said receiving station or into said variable control meansat said remote control station.

3. In a remote control system, a receiving station, a remote controlstation, a line wire circuit, connections between one end of said linewire circuit and said receiving station, connections between the otherend of said line wire circuit and said remote control station, signalindicating means at said remote control station electrically connectedwith said line wire circuit, a beat frequency oscillator at saidreceiving station connected with said line wire circuit, a source ofplate potential at said remote station for said oscillator, meanslocated at said remote control station and connected with said line wirecircuit for controlling the efiective plate potential supplied to saidoscillator, and means in each of the aforesaid connections for excludingsaid plate potential therefrom.

4. In a remote control system, a receiving station, a remote controlstation, a line wire circuit, connections between one end of said linewire circuit and said receiving station, connections between the otherend of said line wire circuit and said remote control station, audiofrequency signal indicating means located at said remote control stationand responsive to audio frequency signals transmitted over said linewire circuit, a beat frequency oscillator located at said receivingstation, connections between said beat frequency oscillator and saidline wire circuit, a source of plate potential at said remote stationfor said oscillator, means located at said remote control station forcontrolling the effect of said plate potential upon said oscillator,connections between said means and said line wire circuit, means in thefirst two of the aforesaid connections for preventing the passage ofplate potential, and means in the last two of the aforesaid connectionsfor preventing the passage of audio frequency signal energy.

5. In a remote control system, a receiving station, a remote controlstation, a line wire circuit extending therebetween for transmittingaudio frequency signals from said receiving station to said remotecontrol station, signal indicating means connected with said line wirecircuit for reproducing the signals transmitted from said receivingstation, 'a beat frequency oscillator at said receiving station,connections between said oscillator and said line wire circuit, a platecircuit for said oscillator including a source of potential at saidremote station, and a potentransmitting from said receiving station tothe remote control point audio frequency signalling energy andsimultaneously transmitting in the opposite direction from the remotecontrol point to said receiving station direct current for controllingthe frequency of oscillations generated by said oscillator.

PERCIVAL D. LOWELL.

